ISLAMABAD, Pakistan (CNN) -- A suicide truck bombing destroyed the packed Marriott Hotel, near the Parliament building and the prime minister's home, in the city of Islamabad, Pakistan, on Saturday night.

The attack killed at least 40 people and wounded another 200, police said.

People were still trapped in the hotel, which burst into flames after the explosion caused a natural gas pipe leak, officials said.

Details and the number of fatalities are still unclear because of conflicting initial reports. One or two vehicles was involved in the attack.

The gas leak set the top floor of the five-story, 258-room hotel on fire, police said, and the blaze quickly engulfed the entire structure.

The Marriott, a Western brand-name hotel, has been the site of attacks in the past, said CNN's Peter Bergen. See where the attack occurred »

Pakistani security officials collect evidence from the estimated 10-meter (33-foot)-deep crater at the Marriott Hotel on Saturday.